I said to all to use recirculating hood not vented but was asked what if we used this? Obviously I don't want to compromise our near passive standards.

Edited May 6, 20242 yr by CalvinHobbes

Why?

 

You really don't need any cooker hood on daily basis with MVHR it does all the work. You only really need it occasionally.

Agreed. Fit a recirculating hob that vents to the room for the occasional time you need it and MVHR for everything else. 

Those chinesium dampers may not seal off terribly well and are a pain to try to interface as they're live to open/ live to close. A spring return one would be handier...

If the MVHR has an extract point in the kitchen put a filter pad in it.

 

We change ours at least every six months and it is amazing what grease and crud it catches that would otherwise be deposited on the inside of the ducting and the HR heat exchanger. Ditto bathrooms to catch towel fluff.

 

HX in central plant then stays squeaky clean, as it is in ceiling void over stairwell this reduces need for servicing off an extending ladder.

2 hours ago, sharpener said:

If the MVHR has an extract point in the kitchen put a filter pad in it.

 

Is that a standard fitting, an extraction point with a filter pad in it, or did you fab it your self?

DIY

 

The kitchen has a 6 in self-closing fire register, this has a big lyre-shaped loop of temperature-sensitive Shape Memory Alloy above it so we tailor a disposable "hat" of bonded actate fibre to go over it, John Lewis sell a self-extinguishing grade in their uphostery materials dept. OH usually makes several at a time from a cardboard template.

 

The bathroom registers are plain 4 in circular with an adjustable centre damper. We cut 4 in circles of BAF and use two thicknesses, discarding the dirty (lower) one and fitting the new one over the central adjusment screw on the clean (upper) side every 6 months.

 

I usually remember to (a) turn off the system while I do this so stray stuff is not sucked upwards and (b) put a flexible duster (hamster-on-a-stick type) up the duct and back with a twisting motion but it's usually pretty clean anyway.

 

Villavent instructions are to clean all the ductwork with a wet pull-through every ?5 years, didn't fancy having to do that, much of it is as you would expect rather inaccessible as the solar inverters and narrow roof trusses make the loft impassable in places.

Many people use G3/G4 conical filters in their MVHR extracts - not just in the kitchen to catch grease but also in bathrooms to catch lint etc. from towels. These filters are readily available online but you will need to ensure you're still meeting your airflow requirements when fitted.

 

Example - https://www.paulheatrecovery.co.uk/product/filter-cone-125/

 

It is all about trade-offs. You can still have an external venting cooker hood, but it needs to have an airtight seal and be insulated, so as not to affect the MVHR effectiveness and add heat loss.

 

Passive house Institute has a general guideline on this topic. 
 

https://passiv.de/downloads/05_extractor_hoods_guideline.pdf

1 hour ago, LnP said:

Is that a standard fitting, an extraction point with a filter pad in it, or did you fab it your self?

Standard fitting as we have one 

1 hour ago, garrymartin said:

These filters are readily available online but you will need to ensure you're still meeting your airflow requirements when fitted.

 

Thanks. Surprised Villavent don't offer as standard then.

 

Will think about it again when we are about to run out of stock material. Availability has been a problem in the past but we have quite a lot atm.

 

Have had a duff experience buying replacement filters online for the central unit, they came without the foam sealing tape round the periphery so then had to source that separately. And they are relatively expensive so prolonging the life with filters at the inlets is worth doing.

 

Have no idea how restrictive the BAF wadding is, but it seems very easy to breathe through with no noticeable restriction, that's partly why we use two thicknesses in the bathrooms. But only one in the kitchen as the airborne grease spatter seems to coat the filter material which makes it better at capturing other particles.

 

Overall am pleased with the results. Is less of a hassle than many other routine maintenance tasks e.g. replacing batteries in alarms and wireless TRVs which I always seem to be doing, they fail according to usage so a campaign once a year might still not be often enough for some.

1 hour ago, garrymartin said:

Many people use G3/G4 conical filters in their MVHR extracts - not just in the kitchen to catch grease but also in bathrooms to catch lint etc. from towels. These filters are readily available online but you will need to ensure you're still meeting your airflow requirements when fitted.

 

Example - https://www.paulheatrecovery.co.uk/product/filter-cone-125/

 

I use similar to those in all my extraction points, it's amazing the amount of stuff they collect in 6 months, and makes you wonder how contaminated the ducts would be if not using them. The main MVHR extraction side filter is almost always clean when I inspect.

1 hour ago, garrymartin said:

Many people use G3/G4 conical filters in their MVHR extracts - not just in the kitchen to catch grease but also in bathrooms to catch lint etc. from towels. These filters are readily available online but you will need to ensure you're still meeting your airflow requirements when fitted.

 

Example - https://www.paulheatrecovery.co.uk/product/filter-cone-125/

 

Do these conical filters fit into any 125 mm extract point or do they require a particular fitting?

I'm not aware that they require a particular fitting or are specific to a particular terminal or manufacturer. Here's an example of a filter change in a Zehdner terminal to give you an idea...

 

 

21 minutes ago, LnP said:

Do these conical filters fit into any 125 mm extract point or do they require a particular fitting?

Yes, I just slip them on the spring prongs that hold the terminal in place